1. Field of the Invention
The present invention generally relates to digital compositing. More specifically, the present invention relates to a method for real-time compositing of encrypted video streams without decryption.
2. Description of the Related Art
The transmission of digital video has become more commonplace with the standardization of digital video interfaces such as Displayport, HDMI and DVI. Likewise, the encryption of transmitted video has also become more commonplace. The encryption of over-the-cable video has created a problem for people who wish to composite video (e.g. picture-in-picture, or PIP) in real-time. Since the introduction of encrypted video, the market for non-display devices that can composite encrypted digital video has been non-existent.
The obvious method for compositing video would be to decrypt each of the video streams, perform the compositing operation, and then re-encrypt the streams. However, this creates an issue with copyrights and the Digital Millennium Copyright Act (DMCA), as it is infeasible to obtain express permission from every potential copyright holder to decrypt video simply for the purpose of a compositing operation. The only allowed reason to decrypt video is for the lawful presentation of the video upon a display device; hence it has been infeasible to build over-the-cable compositors that operate on encrypted video upstream of a display device.
General definitions to be used in the present application include the following.
High-Definition Multimedia Interface (“HDMI”) is a compact audio/video interface for transmitting uncompressed digital data.
Transition-minimized differential signaling (“TMDS”) is a technology for transmitting high-speed serial data and is used by the DVI and HDMI video interfaces, as well as other digital communication interfaces.
High-bandwidth Digital Content Protection (“HDCP”) is a digital protection to prevent copying of digital audio and video content as the content is transmitted from one device/source to another. Intel Corporation has published HDCP Specification along with several Revisions which detail techniques for protecting digital content to be transmitted from a source device to a presentation device. In September of 2010, an HDCP master key that allows for the generation of valid device keys was released to the public.
Red, Green, Blue (“RGB”) color model is the adding of the three colors together to produce a wide array of colors, and the RGB color model is used for the sensing, representation, and display of images in electronic systems, such as televisions and computers.
Display Data Channel (“DDC”) is a collection of digital communication protocols between a computer and a graphics display that enables the display to communicate supported display models to an adapter and to enable the computer host to adjust monitor parameters, such as brightness and contrast.
Genlock is a common technique where the video output of one source, or a specific reference signal from a signal generator is used to synchronize other television picture sources together.
Chromeless browser is a web browser wherein the scroll bars and title bar are hidden off screen.
Musunuri et al., U.S. Patent Publication Number 20090213267 for a Video Synchronization System, discloses genlocking one or more video sources based on a generated clock signal.
Larson, U.S. Patent Publication Number 20090141800 for Transmitting Video Streams, discloses coordinating the transmission of intra-frames of a first video stream with transmission of intra-frames of a second video stream.
Aleksic et al., U.S. Patent Publication Number 20080278606 for Image Compositing, discloses a video image received in portions, combined with a second image and encoded.
Kalva et al., U.S. Patent Publication Number 20100158099 for Systems And Method For Video/Multimedia Rendering, Composition, And User Interactivity, discloses presenting a multimedia element with and during a decoding of an encoded video.
Anderson, U.S. Patent Publication Number 20100248817 for Streaming Video For Electronic gaming Machines With Real-Time Interactive Control discloses real-time compositing video images with local images for gaming.
Gorzynski et al., U.S. Patent Publication Number 20110025819 for Compositing Video Streams, discloses compositing video streams for video conference.
Gausereide, U.S. Patent Publication Number 20110008017 for Real Time Video Inclusion System, discloses compositing in real time a local video stream from a web camera with an external video feed, for commercial advertising purposes.
Reinoso et al., U.S. Patent Publication Number 20090225983 for a System And Method For Improved Processing And Decoding Of An Encrypted Digital Video Signal, discloses storing the location of an encryption portion of a video stream in an unencrypted portion of the video stream to facilitate the efficient location and use of the encrypted portion of the video stream.
Therefore, in order to create a practical solution that can be broadly deployed and not run afoul of copyright issues, all incoming video sources must be synchronized and encrypted to the same key, and the compositing must happen in the cipher text domain with no involvement of decryption.